A defiant Barack Obama challenged his Republican opponent over which presidential candidate would keep the U.S. safer, delivering a sharp rebuke to John McCain's aides who said the Democratic challenger had a naive approach toward fighting terrorism.

A defiant Barack Obama said Tuesday he would take no lectures from Republicans on which candidate would keep the U.S. safer, a sharp rebuke to John McCain's aides who said the Democrat had a naive, Sept. 10 mind-set toward terrorism.

A defiant Barack Obama said Tuesday he would take no lectures from Republicans on which candidate would keep the U.S. safer, a sharp rebuke to John McCain's aides who said the Democrat had a naive, Sept. 10 mind-set toward terrorism.